Governmental regulations provide safety specifications for many automotive components. The National Highway Traffic Safety Administration (“NHTSA”) is one government agency that sets and enforces safety performance standards for motor vehicles and motor vehicle equipment. In addition to government imposed standards, consumer desires also place pressure on automobile manufacturers and suppliers to increase the safety of motor vehicles. Improved vehicle designs regarding impact resistance have undoubtedly saved many lives and decreased serious injury. Improvements in side impact resistance have attracted significant attention due to the enhanced potential of injury during side impact. FMVSS 214 is a governmental standard promulgated by NHTSA regarding side impact protection.
FIG. 1 provides a side view of a door assembly that utilizes foam for side impact resistance. In FIG. 1, the trim panel is removed in order to allow viewing of the relevant structures. Door assembly 10 includes foamed pad 12 which is attached to door bolster 14 and upper door frame 16. Typically, an adhesive is used for this attachment. The position in door assembly 10 at which foamed pad 12 is placed is specified by governmental regulation. In general, this position is at a position that a vehicle occupant is most likely to strike during side impact. FIG. 2 provides an illustration of the performance of foamed pad 12 after a chest impact. Although foamed pad 12 is clearly compressed the dependence of the compression as a function of the force is subject to regulation and to specification by the automobile manufacturers. Displacement d1 provides a measure of the amount of compression that foamed pad 12 has undergone. Specifically, displacement d1 is the distance the surface 18 of foamed pad 12 has moved during impact relative to surface 20. In FIG. 2, the original position of surface 18 is shown as a phantom after impact with surface 18′ indicating the actual position after impact. Displacement d1 may be determined as an average for foamed pad 12 or as a measure value for any predetermined position on foamed pad 12. In general, there is a continuous relationship between the reaction force and the displacement such that it is required that the reaction force experienced by the occupant at any point through displacement d1 be less than a specified value. This force value for the door trim level is usually specified by the OEM. For example if force requirement is below 8 N, throughout 10 mm displacement on the force displacement curve the force can never go higher than 8 N. In addition to the force being low, the door trim panel has to absorb its share of the energy generated due to impact. At a certain displacement, a higher force value indicates higher energy absorption which goes against the requirement to keep force low. These two conflicting requirements are address in the present invention by bracket design.
Although the prior art methods of countering side impacts have worked well, there are several issues requiring improvement. As stated above, such foamed layers are typically attached with adhesives. Such adhesives tend to allow somewhat imprecise positioning while requiring time to cure. Moreover, foamed pads tend to be expensive because such pads are formed from specially tailored formulations that cure into pads with the specified impact resistance.
Accordingly, there is a need in the prior art for improved side impact countermeasures.